It is known that indium selenide (In2Se3) possesses at least five different phases α, β, γ, δ, and κ with a (hexagonal layered structure with 1.3 eV band gap) and γ (defective wurtzite structure with 2 eV band gap) being the most stable phases at room temperature. In2Se3 offers promise in applications for optoelectronic devices, non-volatile phase change memory, and energy storage. Further, due to its similar crystal structure and small lattice mismatch, In2Se3 is a compatible template for growth of prototypical 3D topological insulator (TI) Bi2Se3. This holds great importance since interfacial and bulk defects have remained a major obstacle for further progress in the field of TIs since their discovery; and thus, having a chemically inert substrate with a small lattice mismatch is a key step toward suppressing these defects and eventually realization of functional TI devices for application in quantum computation and spintronics.
However, a reliable way to grow high quality single crystalline In2Se3, essential for esoteric fundamental physics studies as well as future technology, is still missing. This is because In2Se3 grows in a polymorphic fashion on current commercially available substrates, such as sapphire (Al2O3) and strontium titanate (SrTiO3). Even in the attempt by Rathi et al. “Optimization of In2Se3/Si(111) Heteroepitaxy To Enable Bi2Se3/In2Se3 Bilayer Growth” Cryst. Growth Des. 14, 4617-4623 (2014), the MBE growth of In2Se3 on H-passivated Si(111), which has a lower lattice mismatch, led to a disordered interface.